1Generating patches with -p 2-------------------------- 3 4When "git-diff-index", "git-diff-tree", or "git-diff-files" are run 5with a `-p` option, "git diff" without the `--raw` option, or 6"git log" with the "-p" option, they 7do not produce the output described above; instead they produce a 8patch file. You can customize the creation of such patches via the 9`GIT_EXTERNAL_DIFF` and the `GIT_DIFF_OPTS` environment variables. 10 11What the -p option produces is slightly different from the traditional 12diff format: 13 141. It is preceded with a "git diff" header that looks like this: 15 16 diff --git a/file1 b/file2 17+ 18The `a/` and `b/` filenames are the same unless rename/copy is 19involved. Especially, even for a creation or a deletion, 20`/dev/null` is _not_ used in place of the `a/` or `b/` filenames. 21+ 22When rename/copy is involved, `file1` and `file2` show the 23name of the source file of the rename/copy and the name of 24the file that rename/copy produces, respectively. 25 262. It is followed by one or more extended header lines: 27 28 old mode <mode> 29 new mode <mode> 30 deleted file mode <mode> 31 new file mode <mode> 32 copy from <path> 33 copy to <path> 34 rename from <path> 35 rename to <path> 36 similarity index <number> 37 dissimilarity index <number> 38 index <hash>..<hash> <mode> 39+ 40File modes are printed as 6-digit octal numbers including the file type 41and file permission bits. 42+ 43Path names in extended headers do not include the `a/` and `b/` prefixes. 44+ 45The similarity index is the percentage of unchanged lines, and 46the dissimilarity index is the percentage of changed lines. It 47is a rounded down integer, followed by a percent sign. The 48similarity index value of 100% is thus reserved for two equal 49files, while 100% dissimilarity means that no line from the old 50file made it into the new one. 51+ 52The index line includes the SHA-1 checksum before and after the change. 53The <mode> is included if the file mode does not change; otherwise, 54separate lines indicate the old and the new mode. 55 563. Pathnames with "unusual" characters are quoted as explained for 57 the configuration variable `core.quotePath` (see 58 linkgit:git-config[1]). 59 604. All the `file1` files in the output refer to files before the 61 commit, and all the `file2` files refer to files after the commit. 62 It is incorrect to apply each change to each file sequentially. For 63 example, this patch will swap a and b: 64 65 diff --git a/a b/b 66 rename from a 67 rename to b 68 diff --git a/b b/a 69 rename from b 70 rename to a 71 72 73combined diff format 74-------------------- 75 76Any diff-generating command can take the `-c` or `--cc` option to 77produce a 'combined diff' when showing a merge. This is the default 78format when showing merges with linkgit:git-diff[1] or 79linkgit:git-show[1]. Note also that you can give the `-m` option to any 80of these commands to force generation of diffs with individual parents 81of a merge. 82 83A 'combined diff' format looks like this: 84 85------------ 86diff --combined describe.c 87index fabadb8,cc95eb0..4866510 88--- a/describe.c 89+++ b/describe.c 90@@@ -98,20 -98,12 +98,20 @@@ 91 return (a_date > b_date) ? -1 : (a_date == b_date) ? 0 : 1; 92 } 93 94- static void describe(char *arg) 95 -static void describe(struct commit *cmit, int last_one) 96++static void describe(char *arg, int last_one) 97 { 98 + unsigned char sha1[20]; 99 + struct commit *cmit; 100 struct commit_list *list; 101 static int initialized = 0; 102 struct commit_name *n; 103 104 + if (get_sha1(arg, sha1) < 0) 105 + usage(describe_usage); 106 + cmit = lookup_commit_reference(sha1); 107 + if (!cmit) 108 + usage(describe_usage); 109 + 110 if (!initialized) { 111 initialized = 1; 112 for_each_ref(get_name); 113------------ 114 1151. It is preceded with a "git diff" header, that looks like 116 this (when `-c` option is used): 117 118 diff --combined file 119+ 120or like this (when `--cc` option is used): 121 122 diff --cc file 123 1242. It is followed by one or more extended header lines 125 (this example shows a merge with two parents): 126 127 index <hash>,<hash>..<hash> 128 mode <mode>,<mode>..<mode> 129 new file mode <mode> 130 deleted file mode <mode>,<mode> 131+ 132The `mode <mode>,<mode>..<mode>` line appears only if at least one of 133the <mode> is different from the rest. Extended headers with 134information about detected contents movement (renames and 135copying detection) are designed to work with diff of two 136<tree-ish> and are not used by combined diff format. 137 1383. It is followed by two-line from-file/to-file header 139 140 --- a/file 141 +++ b/file 142+ 143Similar to two-line header for traditional 'unified' diff 144format, `/dev/null` is used to signal created or deleted 145files. 146+ 147However, if the --combined-all-paths option is provided, instead of a 148two-line from-file/to-file you get a N+1 line from-file/to-file header, 149where N is the number of parents in the merge commit 150 151 --- a/file 152 --- a/file 153 --- a/file 154 +++ b/file 155+ 156This extended format can be useful if rename or copy detection is 157active, to allow you to see the original name of the file in different 158parents. 159 1604. Chunk header format is modified to prevent people from 161 accidentally feeding it to `patch -p1`. Combined diff format 162 was created for review of merge commit changes, and was not 163 meant for apply. The change is similar to the change in the 164 extended 'index' header: 165 166 @@@ <from-file-range> <from-file-range> <to-file-range> @@@ 167+ 168There are (number of parents + 1) `@` characters in the chunk 169header for combined diff format. 170 171Unlike the traditional 'unified' diff format, which shows two 172files A and B with a single column that has `-` (minus -- 173appears in A but removed in B), `+` (plus -- missing in A but 174added to B), or `" "` (space -- unchanged) prefix, this format 175compares two or more files file1, file2,... with one file X, and 176shows how X differs from each of fileN. One column for each of 177fileN is prepended to the output line to note how X's line is 178different from it. 179 180A `-` character in the column N means that the line appears in 181fileN but it does not appear in the result. A `+` character 182in the column N means that the line appears in the result, 183and fileN does not have that line (in other words, the line was 184added, from the point of view of that parent). 185 186In the above example output, the function signature was changed 187from both files (hence two `-` removals from both file1 and 188file2, plus `++` to mean one line that was added does not appear 189in either file1 or file2). Also eight other lines are the same 190from file1 but do not appear in file2 (hence prefixed with `+`). 191 192When shown by `git diff-tree -c`, it compares the parents of a 193merge commit with the merge result (i.e. file1..fileN are the 194parents). When shown by `git diff-files -c`, it compares the 195two unresolved merge parents with the working tree file 196(i.e. file1 is stage 2 aka "our version", file2 is stage 3 aka 197"their version").